ST. LOUIS (AP) -- Mississippi River shipping was halted Tuesday north of St. Louis after a barge got caught up on an auxiliary lock's gate at one of the waterway's busiest points, causing a swelling barge jam that could persist into the week, the Army Corps of Engineers said.

Corps spokesman Mike Petersen said the accident happened about 5 a.m. in the 600-foot-long lock near Granite City, Ill., that had been pressed into greater duty since the adjacent main lock -- twice the length of the damaged one -- began undergoing repairs early last month.

Corps crews were scrambling later Tuesday to map out how to fix the damaged auxiliary lock, figuring "it most likely will be closed a day or two" to barge traffic in both directions, Petersen said.

"We don't have a full picture on that until we have a plan in place" to make the repairs, he said.

Coast Guard Lt. Colin Fogarty said that while no one was injured in the accident, the closure of Lock and Dam 27 had forced 11 southbound and five northbound tows with a combined 87 barges to park there and await passage.

Tuesday's accident was the latest headache for the Army Corps at the lock, coming five months since a barge split open a protection cell -- a rock-filled steel cylinder against which barges rub to help align them for proper entry into the lock -- at the main lock. That spilled enough of the rock into the river to obstruct passage, closing that site for five days and stranding hundreds of barges.

That September damage was on an unarmored section of the vertical protection cell that the barges don't typically make contact with because they're often 15 to 20 feet under water. But that portion was exposed because the river's level had been lowered dramatically by the nation's persisting drought, the Army Corps of Engineers said.

Corps crews made a temporary fix to that problem in September, then closed the main gate last month for ongoing, regularly scheduled repairs and remove the weakened protection cell, Petersen said.

Roughly half of the nation's farm exports pass through that lock, making any shutdown worrisome.

Coast Guard and Army Corps officials estimated the September closure of the lock, through which 73 million tons of cargo typically pass each year, stood to cost the shipping industry $2 million to $3 million a day in lost revenue. The economic impact of the latest closure at the lock wasn't immediately clear and would depend on how long that site was closed to shipping.